Electrical Conduction Please click the links below for full discussions of this subject. This animation includes a large block of material at the top where both ions and electrons are shown as well as a pipe (conducting wire) connecting the two ends of the large block. The wire shows no ions because of space restrictions but it's really the similar to the conducting version of the large block and is just there to show the difference in electron current for the various conditions. Although electrical conduction in solids depends strongly on the quantum behavior of atoms when they are closely spaced, the particle model depicted here gives an intuitive concept of why some materials are better conductors than others and why temperature increases in good conductors actually decrease conductivity while in semiconductors they increase conductivity. The (red) ions' vibration amplitude increases as temperature increases and this causes more conductor electrons to be scattered as they make their way from the left end to the right end of the big block thererby reducing the conductivity slightly (see the third link below). Conductivity also depends on whether electrons are bound to their parent atoms or not. Binding is depicted as the electrons circling their parent atoms. For a conductor, all electrons are free from their parents and therefore their domain is the entire conductor and that produces good conductivity. When the temperature rises, the parent (red) ions vibrate around their original sites at higher amplitudes. The primary limits to conductivity are the free electrons running into the vibrating ions. If there were no thermal vibrations, conductivity of metal crystals without impurities could be almost infinite like that of a superconductor. But, even near absolute zero temperature, the vibrations scatter the electrons. The viewer should notice how, for a semiconductor, the conduction band fills as temperature increases resulting in higher conductivity (more electrons) in the wire. Also, for the semiconductor, note that the fraction of electrons bound to their parents decreases as the temperature increases. The viewer should also notice that the speed of the electrons in the wire increases as the Applied Voltage increases. Electrical current is this speed times the number of electrons per unit length in the wire. The viewer has the following options: 1. Selection of type of conducting material, Conductor, Semiconductor, or Insulator. Schematic diagrams of energy band filling for each are provided. 2. Delection of the number of atoms in the large block 3. Selection of Applied Voltage by using the Volts slider at the bottom of the current loop. 4. Selection of Temperature in degrees Kelvin using the appropriate slider. In a Semiconductor, temperature increases the number of electrons promoted from the Valence Band to the Conduction band, thereby increasing conductivity.
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